public class prefixCode {
  public String isOne( String[] words ) {
    if ( words.length ==  1 )
       return "Yes";
       
  for ( int i = 0; i < words.length; i++ ) {
    for (int j = 0; j < words.length; j++ ) { 
       if( i == j )
         continue;
       else if ( words[i].startsWith(words[j]) )
         return "No, " + Integer.toString(j);
    }
  }
  return "Yes";
  }
}